Supercontinuum fiber lasers, such as those available from Fianium Ltd. of Southampton, UK (e.g., models SC400 and SC450, see www.fianium.com) can deliver “white” or broad bandwidth laser light. A highly non-linear optical medium is pumped with intense laser pump light (usually pulses of light) to generate the supercontinuum.
In certain supercontinuum lasers commercially available today, such as the SC400 and SC450, the source of intense laser pump light is typically a pulsed or ultrafast fiber-delivered laser and the non-linear optical medium is a highly non-linear optical fiber such as a photonic crystal fiber. The output of the pump laser and non-linear fiber are fusion spliced together to produce a homogeneous, continuous optical fiber. This configuration has advantages over free space launching of the pump light into the non-linear fiber through combinations of lenses in terms of reliability and mechanical robustness.
It can be of interest to sample the output of the supercontinuum laser. Such sampling can be desirable, for example, to achieve closed loop control or to monitor the output power to check for degradation or a break in the delivery fiber. Such a break could constitute a safety hazard, and it is preferable than a means is in place for detecting the break. As another example, sampling can often be useful for analyzing or monitoring of the spectral content of supercontinuum or filtered supercontinuum light delivered by an optical fiber. In-situ analysis or monitoring can be used for spectral characterization for real-time calibration of the source or of the illumination light beam when incorporated into instrumentation or experiments.
The output light can be sampled using free space techniques. A partial beam splitter or partially reflective surface can split off a portion of a free space beam, and the split beam can be analyzed using a spectrometer, CCD array, etc. Free-space sampling of the laser output is not convenient for many fiber-based applications, as often a free space beam is only available at the output of the delivery fiber of the supercontinuum source, which is typically positioned remotely from the laser source that houses the electronics and sources of electrical power.
Accordingly, it is an object of the invention to address one or more of the deficiencies of the prior art.